Field of the Invention
The present invention relates to a process for manufacturing a resist composition to be used for fine processing in a process for manufacturing a semiconductor apparatus including a semiconductor device, etc., in particular, to a process for manufacturing a composition for forming a resist film (a resist composition) to be used for a multi-layer resist method, and a patterning process using a resist composition manufactured by the process for manufacturing a resist composition.
Description of the Related Art
Accompanying with high integration and high speed acceleration of an LSI, miniaturization of a circuit pattern size is rapidly progressing. The lithography technology has achieved formation of a fine pattern by shortening wavelength of the light source and selecting an appropriate resist composition thereto, which are to conform to the miniaturization.
However, in the case where miniaturization is performed with the same light source, when the miniaturization is performed with the same film thickness of the photoresist film to be used, i.e., when a pattern width is made smaller, the aspect ratio of the photoresist pattern after development becomes large, and pattern collapse occurs as a result. Thus, the photoresist film thickness has been thinned accompanied by the miniaturization so that the aspect ratio of the photoresist pattern is in an appropriate range. However, due to thinning of the photoresist film, the problem further generated that precision of pattern transfer to a substrate to be processed is lowered.
One of the methods for solving the above-mentioned problems is multilayer resist method. In this method, an under layer film having etching selectivity different from that of a photoresist film, i.e. a resist upper layer film, is interposed between the resist upper layer film and a substrate to be processed, then a pattern is formed on the resist upper layer film, then the pattern is transferred to the under layer film by etching using the upper layer resist pattern as an etching mask, and further the pattern is transferred to the substrate to be processed by etching using the under layer film as an etching mask.
In a silicon-containing resist under layer film or an organic under layer film to be used in such a multi-layer resist method, metal impurities derived from an environment, an apparatus, an equipment and starting materials are generally contained. In the patterning process using the multi-layer resist method, pattern transfer using dry etching is repeatedly carried out, so that such metal impurities become an etching mask under dry etching conditions and are transferred to a body to be processed for a semiconductor apparatus. Thus, when a semiconductor apparatus is manufactured by using the substrate, it shows electrical abnormality such as open abnormality, short-circuit abnormality, etc., in the circuit, which is one of reasons in lowering yield of semiconductor apparatuses. At present, for preventing from the defect, purification of the starting materials is said to be the most effective way and, for example, a method is disclosed in Patent Document 1 that the starting polymer can be purified by contacting with an acidic aqueous solution. However, in the resist composition to be used in the most advanced process which is required to perform fine processing, etc., it is not sufficient only by purification of the polymer.